This invention relates generally to improvements in external or exoskeletal prosthetic devices and systems of the type utilizing an implanted, bone anchored mounting post having or carrying an externally protruding or externally exposed fixator structure for removable attachment of a prosthesis such as a prosthetic limb or the like. More particularly, this invention relates to an antimicrobial containment cap for use in combination with a bone anchored prosthesis mounting system, wherein the containment cap supports and retains a selected antimicrobial agent against the skin of an amputee substantially at the exit site or tissue interface of the fixator structure extending through the skin, to reduce or eliminate risk of infection.
Socket type prosthetic limbs such as prosthetic arm and leg structures for use by amputees are generally well known in the art, wherein a prosthesis is constructed with an open-ended and typically padded socket structure for receiving and supporting the post-surgical stump of a residual amputated limb. By way of example, a socket type prosthetic leg includes such open-ended socket structure at an upper end thereof for receiving and supporting the post-surgical upper leg of a transfemoral amputee. Various straps and/or other fasteners are provided for securing the prosthetic leg to the amputated limb to accommodate walking mobility at least on a limited basis. Such prosthetic limbs can be an important factor in both physical and mental rehabilitation of an amputee.
However, socket type prosthetic limbs are associated with a number of recognized limitations and disadvantages. In particular, the socket style prosthesis inherently couples mechanical loads associated with normal ambulatory activity through a soft tissue interface defined by the soft tissue covering the end or stump of the residual amputated limb, but wherein this soft tissue interface is structurally unsuited for this purpose. While many different arrangements and configurations for the requisite straps and other fasteners have been proposed for improved transmission and distribution of these mechanical loads to bone structures for improved secure and stable prosthesis attachment, to correspondingly accommodate a more natural ambulatory movement, such arrangements have achieved only limited success. In addition, compressive loading of this soft tissue interface often results in blisters, sores, chafing and other undesirable skin irritation problems which have been addressed primarily by adding soft padding material within the socket structure. But such soft padding material undesirably increases the extent of the soft or non-rigid interface between the amputated limb and prosthesis, all in a manner that is incompatible with an optimally secure and stable prosthesis connection. As a result, particularly in the case of a prosthetic leg, traditional socket style connection structures and methods have generally failed to accommodate a normal walking motion.
In recent years, improved external or exoskeletal prosthetic devices have been proposed, wherein the external prosthesis is structurally linked by means of a bone anchored mounting system directly to patient bone. In such devices, a rigid mounting post is surgically implanted and attached securely to patient bone as by means of osseointegration or the like. This implanted mounting post extends from the bone attachment site and includes or it attached to a fixator pin or post structure that protrudes through the overlying soft tissue at the end of the residual amputated limb. Thus, one end of the fixator pin is externally exposed for suitable and secure attachment to a prosthetic limb or the like. In such bone anchored mounting systems, mechanical loads on the prosthetic limb during ambulation are transmitted by the rigid components including the external fixator pin and the implanted mounting post directly to patient bone. As a result, conventional mechanical loading of the soft tissue interface is avoided, and substantially improved and/or normal patient movements are accommodated. In addition, the requirement for compressive loading of the soft tissue at the end of the amputated limb is significantly reduced, to correspondingly reduce incidence of blisters and other associated skin irritation problems.
Although use of a bone anchored mounting system offers potentially dramatic improvements in secure and stable prosthetic limb attachment, and corresponding improvements in amputee lifestyle, the exit site or interface between the externally protruding fixator pin and the soft tissue at the end of the residual limb inherently subjects the amputee to a significant and on-going risk of infection. That is, the soft tissue interface with the externally protruding fixator pin is difficult to seal and protect against entry of microbial infection-producing organisms. The difficulties in adequately sealing this tissue-pin interface are compounded by the presence of multiple and typically random and irregular-shaped small skin folds formed in the soft tissue at the end of the residual limb, and thus present in the immediate vicinity of the tissue-pin interface. These small skin folds unfortunately provide multiple shallow channels or pathways which are difficult to keep clean, many of which lead directly to the tissue-pin interface. Infection at this tissue-pin interface can produce serious complications including eventual loosening and failure of the bone anchored mounting post.
There exists, therefore, a significant need for improvements in and to external or exoskeletal prosthetic devices of the type utilizing a bone anchored mounting system, wherein the risk of infection at the soft tissue interface with an externally protruding fixator pin is substantially reduced and/or eliminated. The antimicrobial containment cap of the present invention fulfills these needs and provides further related advantages.